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2.6 Soil Gas Sampling <br /> After the soil gas probe is adequately purged, samples should be collected by <br /> appropriate methodologies. <br /> 2.6.1 Sample Container: Samples should be collected in gas-tight, <br /> opaque/dark containers (e.g., syringes, glass bulbs wrapped in <br /> aluminum foil, Summa'^" canisters), so that light-sensitive or <br /> halogenated VOCs (e.g., vinyl chloride)will not degrade. <br /> A If a syringe is used, it should be leak-checked before each use by <br /> closing the exit valve and attempting to force ambient air through <br /> the needle. <br /> B. If syringe samples are analyzed within five (5) minutes of <br /> collection, aluminum foil wrapping may not be necessary. <br /> C. EPA Method TO-14A, TO-15, or an equivalent air analysis method, <br /> requires samples be collected in Summalm canisters. <br /> D. If a Summalm canister is used, a flow regulator should be placed <br /> between the probe and the SummaTm canister to ensure the <br /> SummaTm canister is filled at the flow rate as specified in Section <br /> 2.5.2. <br /> E. TedlarTm bags should not be used to collect VOC samples. <br /> F. Specific requirements for methane and hydrogen sulfide sample <br /> containers are specified in Section 2.7.9. <br /> 2.6.2 Sample Collection <br /> A. Vacuum Pump: When a vacuum pump is used, samples should <br /> be collected on the intake side of the vacuum pump to prevent <br /> potential contamination from the pump. Vacuum readings or <br /> qualitative evidence of a vacuum should be recorded on field data <br /> sheets for each sample. <br /> B. Shallow Samples: Care needs to be observed when collecting <br /> shallow soil gas samples to avoid sample breakthrough from the <br /> surface. Extensive purging or use of large volume sample <br /> containers (e.g., SummaTv canisters) should be avoided for <br /> collection of near-surface samples[e.g., shallower than five (5) <br /> feet bgs]. <br /> 01/28/2003 - 12- <br />